1. Field of the Invention
The present invention relates to a dielectric recording/reproducing head, a dielectric recording apparatus, a dielectric reproducing apparatus, and a dielectric recording/reproducing apparatus for recording information with multivalued data in microdomains of a dielectric substance or for reproducing it.
2. Description of the Related Art
As high-density, large-capacity recording/reproducing apparatuses of randomly accessible type, there are known an optical disk apparatus and a hard disk drive (HDD) apparatus. Moreover, a recording/reproducing technique using a scanning nonlinear dielectric microscopy (SNDM) for nanoscale analysis of a dielectric (ferroelectric) substance has been recently proposed by the inventors of the present invention.
Optical recording uses an optical pickup with a laser as a light source. Data is recorded by forming pits that are concavo-convex on a disk surface or by forming the crystal phase in a phase shift medium. The data is reproduced by using the difference in the reflectance between an amorphous phase and a crystal phase or by using magneto optical effect. However, the pickup is relatively large, which is inappropriate for high-speed reading. Also, the size of the recording pit is defined by the diffraction limit of light, so that its recording density is limited to 50 G bit/inch2.
In the longitudinal recording of magnetic recording as represented by the HDD, a magnetic resistance (MR) head has been recently realized by using giant magnetic resistance (GMR). Its recording density is expected to be larger than that of the optical disk by using perpendicular magnetic recording. However, the recording density is limited to 1 T bit/inch2 because of thermal fluctuation of magnetic recording information and the presence of a Bloch wall in a portion in which a code is reversed, even if patterned media are used in view of the above cause.
The SNDM can distinguish the plus or minus of a ferroelectric domain by measuring a non-linear dielectric constant in a ferroelectric material. Moreover, it is known that the SNDM has sub-nanometer resolution with an electrically conductive cantilever having a small probe on its tip, which is used for atomic force microscopy (AFM) or the like.
In the recording/reproducing apparatus using the current SNDM technique, a head is provided with: a probe; an inductor connected with the probe; an oscillator which is also connected with the probe; and a return electrode for returning a high-frequency electric field which is applied from the tip of the probe and then passed through a ferroelectric recording medium. A resonance circuit is formed from a capacitance of the ferroelectric recording medium just under the probe and from the inductor. Data reproduction is performed by detecting changes in oscillation frequency in polarization states in the vertical direction of the surface of the ferroelectric recording medium. Moreover, data recording is performed by applying an electric field from the probe to the ferroelectric recording medium in the vertical direction of the surface of the ferroelectric recording medium and by forming the polarization states corresponding to the data in the vertical direction of the surface of the ferroelectric recording medium. Namely, information recorded in the ferroelectric material is binary data, which is either “0” or “1”, and the information is recorded in the ferroelectric recording medium as polarization directions in the vertical direction of the surface of the ferroelectric recording medium.